[PATCH] <not-for-merge> nfs: fix nfs_parse_mount_options() double kfree()

[Ingo Molnar]

Impact: fix crash

Yinghai Lu reported the following crash:

> mpk12-3214-189-158:~ # sh x
> [   63.198629] ------------[ cut here ]------------
> [   63.202589] kernel BUG at mm/slub.c:2753!
> [   63.202589] invalid opcode: 0000 [#1] SMP
> [   63.202589] last sysfs file: /sys/devices/virtual/net/sit0/type
> [   63.202589] CPU 0
> [   63.202589] Modules linked in:
> [   63.202589] Pid: 10027, comm: mount.nfs Not tainted 2.6.29-07100-g833bb30 #21 Sun Fire X4440
> [   63.202589] RIP: 0010:[<ffffffff802e0015>]  [<ffffffff802e0015>] kfree+0x5a/0xcd
> [   63.202589] RSP: 0018:ffff882042ceb9f8  EFLAGS: 00010246
> [   63.202589] RAX: 0200000000000000 RBX: 0000000000000005 RCX: ffffffff80a7dc1f
> [   63.202589] RDX: ffffe20000000000 RSI: ffffc2000000f470 RDI: ffffe2001c018950
> [   63.202589] RBP: ffff882042ceba18 R08: 0000000000000000 R09: ffffffff811019c0
> [   63.202589] R10: 000000004262ce02 R11: ffff882042ceba18 R12: ffff880800706475
> [   63.202589] R13: ffff882042886000 R14: ffff882042cebbd8 R15: ffff882042cebbf0
> [   63.202589] FS:  00007fac729ed6f0(0000) GS:ffffc20000000000(0000) knlGS:0000000000000000
> [   63.202589] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [   63.202589] CR2: 00007fac72c12000 CR3: 0000001841cbb000 CR4: 00000000000006e0
> [   63.202589] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [   63.202589] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> [   63.202589] Process mount.nfs (pid: 10027, threadinfo ffff882042cea000, task ffff8820434dc290)
> [   63.202589] Stack:
> [   63.202589]  ffff882042ceba18 000000004262ce02 0000000000000005 ffff882042886028
> [   63.202589]  ffff882042ceba58 ffffffff80a7dc1f 000000004262ce02 ffff882042886000
> [   63.202589]  000000004262ce02 ffff882042886000 ffffffff80a7b4a6 ffff882042c9ee18
> [   63.202589] Call Trace:
> [   63.202589]  [<ffffffff80a7dc1f>] xs_destroy+0x67/0xac
> [   63.202589]  [<ffffffff80a7b4a6>] ? xprt_destroy+0x0/0xa7
> [   63.202589]  [<ffffffff80a7b532>] xprt_destroy+0x8c/0xa7
> [   63.202589]  [<ffffffff80a823b2>] ? put_rpccred+0x112/0x131
> [   63.202589]  [<ffffffff8051cdd5>] kref_put+0x65/0x87
> [   63.202589]  [<ffffffff80a7a9a9>] ? rpc_free_client+0x0/0xf9
> [   63.202589]  [<ffffffff80a7b490>] xprt_put+0x23/0x39
> [   63.202589]  [<ffffffff80a7aa7a>] rpc_free_client+0xd1/0xf9
> [   63.202589]  [<ffffffff80a83345>] ? unx_destroy+0x3c/0x57
> [   63.202589]  [<ffffffff8051cdd5>] kref_put+0x65/0x87
> [   63.202589]  [<ffffffff80a7aaa2>] ? rpc_free_auth+0x0/0x69
> [   63.202589]  [<ffffffff80a7aaf0>] rpc_free_auth+0x4e/0x69
> [   63.202589]  [<ffffffff8025b827>] ? __wake_up+0x52/0x75
> [   63.202589]  [<ffffffff8051cdd5>] kref_put+0x65/0x87
> [   63.202589]  [<ffffffff80a7a98e>] rpc_release_client+0x64/0x7f
> [   63.202589]  [<ffffffff80a8061c>] ? rpc_put_task+0xb0/0xcb
> [   63.202589]  [<ffffffff80a7abe0>] rpc_shutdown_client+0xd5/0xf8
> [   63.202589]  [<ffffffff80a7a893>] ? rpc_call_sync+0x63/0x80
> [   63.202589]  [<ffffffff803fc4ab>] nfs_mount+0x11f/0x1bf
> [   63.202589]  [<ffffffff803f3036>] nfs_get_sb+0x4ac/0x82a
> [   63.202589]  [<ffffffff802e8f24>] vfs_kern_mount+0x61/0xbf
> [   63.202589]  [<ffffffff802fea1d>] ? get_fs_type+0x58/0xc5
> [   63.202589]  [<ffffffff802e9015>] do_kern_mount+0x56/0x108
> [   63.202589]  [<ffffffff80302195>] do_mount+0x729/0x788
> [   63.202589]  [<ffffffff80300025>] ? copy_mount_options+0xdf/0x155
> [   63.202589]  [<ffffffff8030228c>] sys_mount+0x98/0xf8
> [   63.202589]  [<ffffffff80230d6b>] system_call_fastpath+0x16/0x1b
> [   63.202589] Code: 0c 48 ba 00 00 00 00 00 e2 ff ff 48 6b c0 38 48 8d 3c 10 48 8b 07 f6 c4 40 74 04 48 8b 7f 10 48 8b 07 84 c0 78 10 f6 c4 60 75 04 <0f> 0b eb fe e8 90 75 fd ff eb 4c 48 8b 4d 08 4c 8b 4f 10 9c 5b
> [   63.202589] RIP  [<ffffffff802e0015>] kfree+0x5a/0xcd
> [   63.202589]  RSP <ffff882042ceb9f8>
> [   63.524555] ---[ end trace cd0d38e02ad11d61 ]---

Pekka observed that a bogus pointer was passed to kfree().

This commit:

  a67d18f: NFS: load the rpc/rdma transport module automatically

Moved a kfree() of the options strings in nfs_parse_mount_options()
inadvertently and introduced a double kfree(). Fix it.

Reported-by: Yinghai Lu <yinghai@xxxxxxxxxx>
Analyzed-by: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
 fs/nfs/super.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index a2c18ac..482a2c3 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -1231,6 +1231,7 @@ static int nfs_parse_mount_options(char *raw,
 				goto out_nomem;
 			token = match_token(string,
 					    nfs_xprt_protocol_tokens, args);
+			kfree(string);
 
 			switch (token) {
 			case Opt_xprt_udp:
@@ -1262,7 +1263,6 @@ static int nfs_parse_mount_options(char *raw,
 				goto out_nomem;
 			token = match_token(string,
 					    nfs_xprt_protocol_tokens, args);
-			kfree(string);
 
 			switch (token) {
 			case Opt_xprt_udp:

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